isUsePairedConnections

Returns true if TcpCommunicationSpi should
maintain connection for outgoing and incoming messages separately.
In this case total number of connections between local and some remote node
is getConnectionsPerNode() * 2.

getSelectorSpins

Defines how many non-blocking selector.selectNow() should be made before
falling into selector.select(long) in NIO server. Long value. Default is 0.
Can be set to Long.MAX_VALUE so selector threads will never block.